GapSense unclogs WiFi channels

PORTLAND, Ore. ó The Wireless Association--formerly the Cellular Telephone Industry Association (CTIA)--claims that there are more WiFi enabled smartphones, laptops and tablets in the U.S. than there are people--321 million compared to a population of 315 million. And that doesn't even count the millions of Bluetooth and ZigBee devices all competing in the same 2.4-GHz band. As a result, what is becoming an epidemic problem--interference among these devices--threatens to slow adoption of wireless devices. However, help is on the way in the form of a proposed new technology called GapSense--a new collision avoidance technique to be proposed this week by electrical engineers at the IEEE International Conference on Computer Communications 2013 (April 14-19, Turin, Italy).

In his paper entitled "GapSense: Lightweight Coordination of Heterogeneous Wireless Devices," University of Michigan EE professor Kang Shin, will describe a universal protocol that monitors the energy pulses and gaps on the 2.4-GHz band in order to reduce collisions by as much as 88 percent.

"These devices don't have a direct means of communicating, since they use different protocols," said Shin. "That could be the Tower of Babel for an increasingly diversified world of wireless devices."

University of Michigan Professor Kang Shin has invented a technique called GapSense that nixes the problem of interference among different types of wireless devices operating on the same band. SOURCE: University of Michigan

Even among 2.4-GHz wireless devices that already use the carrier sense multiple access (CSMA) protocol, which listens for radio silence before transmitting, collisions are still commonplace. The problem is that with so many devices in operation, each has a different time delay between listening and transmitting. Thus despite their use of CSMA, collisions are inevitable as each delays by a different amount of time before transmitting into a previously clear channel. In fact, with just moderate WiFi traffic, the researchers estimate that 45 percent of wireless data transmissions involve a collision. However, by switching to its GapSense method, collisions can be reduced to under 8 percent, according to the researchers published results.

Energy is also reduced by as much as 44 percent when using GapSense, according to the researchers, since it separates faster-clocked WiFi transmitters from low-speed units to which it sends a wake-up signal, thus allowing them to catch intended information packets without having to standby listening for as long.

Different protocols prevent devices from hand-shaking with each other--the hidden terminal problem--but GapSense uses virtual carrier sensing to determine when it is clear to transmit regardless of the communications protocol being used.Click on image to enlarge.

Shin, who performed the research with doctoral candidate Xinyu Zhang, now a professor at the University of Wisconsin (Madison), will reveal all the details of the GapSense universal technique at the conference, which they claim solves the problem regardless of which wireless protocols are being used by transmitters and receivers. Funding was provided by the National Science Foundation (NSF).

Has the simple solution already been implemented across the industry: check to identify the least used channel and move there? It seems to me that WiFi devices only use one or two of the available channels.